Various devices have been employed for maintaining predetermined levels of liquids, slurries and the like in tanks and other containing vessels. Float mechanisms and pressure responsive devices have been used for this purpose; these devices include electrical resistance controlled systems, air pressure controlled systems and devices such as the so called "bubbler" controls, which involve the release of gas into the liquid or slurry at selected distances below the surface. While these devices have been satisfactory for a wide range of applications, they involve problems in many applications in which contamination of the liquid or slurry must be avoided. Accordingly, it is an object of this invention to provide an improved device for controlling the level of liquids, slurries and the like.
It is another object of this invention to provide a liquid level control system including a level responsive device having an improved arrangement for preventing contamination of the liquid by the operation of the device.
It is another object of this invention to provide an improved liquid level sensing device for activation of air pressure actuated level control systems.
It is a further object of this invention to provide an improved, reliable and highly sensitive liquid level probe or sensing device for a system for controlling the level of a liquid, or a slurry or the like.